The present invention relates to a process for producing carbon fiber fabrics.
As methods for producing carbon fiber fabrics there are known a method of weaving carbon fibers as a finished product and a method in which an intermediate product is subjected to weaving and the resulting fabric is carbonized or graphitized. As an example of the latter there is disclosed in Japanese patent Laid-Open No. 120136/1988 a three-dimensional fabric containing a pitch based carbon fiber as one component thereof, the carbon fiber having, before heat treatment in a relaxed state, a strength of 15 to 250 kg/mm.sup.2, an elongation to failure of 0.5% to 8.0% and an elastic modulus of 400 to 40,000 kg/mm.sup.2, but, after the said heat treatment, capable of increasing in both strength and elastic modulus to 1.1 times as high as the strength and elastic modulus before the heat treatment and capable of becoming in strength 150 kg/mm.sup.2 or higher and in elastic modulus 40,000 kg/mm.sup.2 or higher. However, fuzzing is apt to occur because of deficient tensile strength.
In Chemical Abstracts Vol. 111, No. 24892d there is disclosed a process for producing a carbon fiber fabric which process comprises infusibilizing pitch fibers from an optically anisotropic pitch, followed by heat treatment at 300.degree.-800.degree. C., then making the resulting carbon fibers having a tensile strength of 0.4 GPa and an elongation at break of 1.5% into a fabric, followed by lamination and subsequent calcining at 2,500.degree. C. However, fuzz is apt to occur because of the use of low heat treatment temperature before weaving, and deficient tensile strength.
In Derwent WPI Acc. No. C 88-328011/46 it is disclosed that, using carbon fibers produced by carbonizing fibers from mesophase pitch at 550.degree.-1,000.degree. C. and having a tensile strength of 20-40 kg/mm.sup.2 and an elongation at break of 1.8-4.0%, a fabric is produced and graphitized. Also in this case, however, fuzz is apt to occur because of low heat treatment temperature before weaving and deficient tensile strength.
And in Japanese Publication No. 20281/1987 there is disclosed a process for producing a carbon fiber product in which as-spun pitch fibers are subjected to an initial carbonization treatment, then a bundle of the fibers is subjected to weaving and the resulting fabric is carbonized or graphitized. Fuzz is apt to occur, however, because of low heat treatment temperature before weaving, and deficient tensile strength.
Further, in Carbon Fiber Reinforced Plastics, Bamberg, West Germany, May 11-12, 1977 there is a description to the effect that infusibilized fibers can be woven if they have a strength of about 40 kg/mm.sup.2 and elongation to failure of 5%, and can be carbonized into a carbon fiber fabric. Fuzz is apt to occur, however, because of low heat treatment temperature before weaving, and deficient tensile strength.
In U.S. Pat. No. 4,138,525 it is disclosed that infusibilized fibers having an elongation at break of 2.1 to 5.6% and a tensile strength of 17,000 to 37,000 psi are made into cloth and carbonized or graphitized. However, fuzzing occurs easily due to low heat treatment temperature before weaving and deficient tensile strength.
In producing fabrics according to the aforementioned conventional methods, there occurs breaking of fibers or fuzzing because the strength of fibers in the weaving stage is not sufficiently high, and therefore even in the resulting fabric is carbonized or graphitized, it is impossible to obtain a high fiber volume fabric. Or there remains permanent strain after carbonization, so the inherent strength cannot be developed when used as a composite material.